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(No Model.) 2 Sheets-Sheet 1.

T. N. VAIL & J. A. SEELY.

TELEPHONE CENTRAL STATION APPARATUS.

No. 894,280. Patented Dec. 11, 1888.

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(No Model.) 7 2 Sheets-Sheet 2. T. N. VAIL & J. A. SEELY.

TELEPHONE CENTRAL STATION APPARATUS.

No. 394,230. Patented Dec. 11, 1888.

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UNITED STATES TELEPHONE-CENTRAL;-

PATENT OFFICE.

AND JOHE A. SEELY, OF

STATION APPARATUS.

SPECIFICATION forming part of Letters Patent No. 394,230, dated December11, 1888.

Application filed August 31, 1888.

To all whom it may concern.-

Be it known that we, THEODORE N. VAIL, of Boston, county of Snifolk, andState of M assachusetts, and JOHN A. SEELY, of the city,

county, and State of New York, have jointly invented certain new anduseful Improvements in Telephone-Central-Station Apparatus, of which thefollowing is a specification.

Our invention relates to the construction and arrangement oftelephone-central-station switch-boards, and is an improvement upon thearrangement of appz-tratus shown, described, and claimed in our LettersPatent dated July 10, 189R, numbered 385,974- and 385,976. a

One feature of improvement consists in a novel arrangement of apparatusfor connecting the circuits assigned to the care of one operator (calledby us a group) with a head telephone, whereby calls maybe receivedwithout preliminary signaling.

e provide the local circuit containing the head telephone with a seriesof spring-jacks. The subscribers circuits terminatein springjack plugs,as described in said patents, and the number of spring-jacks in thelocal circuit is equal to the number of circuits in a group-that is, inthe head telephone local circuit there is a spring-jack for everysubscribers circuit in the group, and the jackplug forming the terminalof every such circuit is normally located in one of these spring- Ijacks. Ye prefer to connect the spring-jacks in multiple are with thehead telephone. \Ve

have also improved the construction and arrangement of keys orpush-buttons for ringing in either of two directions upon a metalliccircuit and for looping in a listening-telephone, with respect to a pairof connected metallic circuits, during the process of conversationbetween the terminal stations. This operation of looping in hasheretofore been practiced by breaking the circuit and inserting alistening-telephone; but the operation of breaking the circuitfrequently produces an interruption,-and in circuits the use of which isfrequently called for the operation Serial No. 284,238. (No model.)

becomes a very serious cause of interruption.

Ourimprovement consists in connecting the terminals of a local circuitcontaining a listening-telephone to opposite sides of a pair of unit-edmetallic circuits. This produces no preliminary break and nointerruption orvariation whatever.

The accompanying drawings illustrate our invention.

Figure 1 is a side view of the apparatus, showing details of the callingand looping-in keys. Fig. 2 is a plan view of the arrange- 0 ment of thehead telephone and group circuits connected in parallel by means of aseries of spring-jacks in a local circuit.

G and G. represent two separate switchboards upon a multiple-boardsystem or arrangement. The metallic circuit 0 0' passes through a jack,j, on board G, through jack j on board G thence through three puslrbuttons, C C- O to be described, and terminates in a spring-jack plug,P, adapted to operate in connection with any of the spring jacks j j Tis an operators head telephone permanently connected into a localcircuit, 19 20.

J is a spring-jack adapted to receive a jaek-plug like P. There are aseries of circuits like 0 csay to the number of one or two thousand, ormore. Of these there are, say, one hundred assigned to the special careof an operator at board G as more fully described in our LettersPatentbeforc referred to. Every circuit of this group of one hundred ofcourse terminates in a plug, P, and there are one hundred spring-jacks,J, connected with the local circuit 19 20. Each plug P is normallylocated in one of these jacks .T. The result is that every circuit ofthe group of one hundred is normally connected with the head telephoneT, and no preliminary signaling is required to get the attention of thecentral- 9o station operator. e prefer to connect the series of jacks Jin multiple are, so that when a plug P is withdrawn the local circuit isnot left open. The special form of springja-ck used by us is normallyopen to avoid 5 short-circuiting the telephone, and is only sists of twostrips, s,which, together with the contacts 1 and 2 in electricalconnection therewith, are firmly fixed to opposite sides of a block ofinsulating material, (Z, which is perforated to form a bearing for therod r, having a button upon its upper end and a wedge-shaped section ofinsulating material, 1 upon its opposite end, acting to force apart thespring-contacts 1 and 2. Near the end of strips 5 s is a block ofinsulating material, f, located in which, at substantially equalintervals, are two pairs or four conducting-contacts, 3 4c 5 0. Thecontactsl and 2 are located in position to make contact with one pair ofsuch contacts, respectively-that is, contact 1 is in position toelectrically unite with either contact 3 or 5, and contact 2 is inposition to electrically unite with either contact 4 or 6. In both casesthe position of 1 and 2, as regards the two pairs of contacts 3 and 5,at and (i, is controlled by the position of the wedge-shaped sectionotinsulatingmaterial, t'.

' The keys (land 0 are for ringing in either of two directions uponconnected metallic circuits. 0 rings in one direction; 0 rings in theother direction. Asouree of electricity, Z), is connected to thecontacts 5 and 6 of each key. The line-circuit c c normallypassesthrough the contacts 1 and 3, 2 and at. The rod 4' being depressed,spreads the contacts 1 and 2 to maintain this connection; but when i iswithdrawn the source of electricity Z) of C is connected into thecircuit entering from one direction. Regarding 0' when i is withdrawn,the source of electricity 1) is connected into the circuit entering fromthe opposite direction. The drawings show the apparatus in a normalposition. If C be operated, circuit will be m c, s, 1, 5, b, 6, 2, s, c.If (1" be operated, the circuit 0 0' will be left open, and the circuitentering by flexible cord m will pass through 0 cm elements 8, 2, (3,12,5, 1, s, and out rz'a m, it being assumed that P and on have beenconnected with a called-for circuit. 7

The key 0 is used to loop the telephoneset L 1 intoconnected circuits.The contacts 3 and 4 for this purpose are dead and useless, and a keywith four contacts instead of six is all that is required; but for thepurpose of preserving uniformity and interchangeability the sameconstruction of key has been used. The telephone-set L 1 is in localcircuit 90 91, connected to the terminals 5 and 6 of key C the strip sisconnected to c, and the strip 5 is connected to Upon operating 0 thecircuit 90 91 is connected to opposite sides of the metallic circuit,and it is therefore in parallel circuit with thetelephonesets atopposite terminals of the connected metallic circuit-s, and theconversation passing between the terminal stations is audible to thecentral-station operator, but no interruption occurs.

llVhat we claim, and desire to secure by Let- H ters Patent, is-

1. The combination of a central station, a series of sub-stations, aseries of electrical circuits, one for each sub-station, atelephoneinstrument for each circuit at the sub-station, a telephone ina local circuit at the central station, a series of normally-openspringjacks in said circuit connected in parallel, and a series ofjack-plugs, one for each substation circuit,.for connecting anddisconnecting each sub-station circuit with said local circuit in.parallel circuit, substantially as described.

2. The combination, at a telephone central station, of an electricalcircuit and a key or push-button for ringing or signaling a substation,consisting of a pair of fixed contacts, a pair of movable contacts, aninsulatingwedge normally located between and forcing the movablecontacts into connection with said fixed contacts to complete thecircuit, and a second pair of fixed contacts forming the terminals of asource of'electricity located in position to connect with said movablecontacts when the wedge is withdrawn, whereby the source of electricityis inserted to ring or signal, substantially as described.

The combination of a central station and a series of sub-stations, aseries of metallic circuits, one for each sub-station, means forconnecting said circuits in pairs at the central station, and a pair ofkeys or push-buttons for inserting a source of electricity with respectto one of such pair of circuits, respectively, each key consisting of apair of fixed contacts, a pair of movable contacts, and aninsulating-wedge located on a movable support normally between and inposition to force said contacts into connection with the pair of fixedcontacts to complete the circuit, and a second pair of fixed contactsforming the terminals of a source of electricity located in position toconnect with said movable contacts When the wedge is withdrawn, wherebythe source of electricity is inserted, substantially as described.

4. The combination of' a central station, a series of sub-stations, aseries of metallic circuits, one for each sub-station, meansforconnecting circuits in pairs, a telephonic instrument at eachsub-station, a telephone in a local circuit at the central station, aseries of switches, one for each circuit, located at the pair ofcontacts, located upon a rod having a central station, each switchconsisting of a reciprocating movement, substantially as de- 10 pair ofcontacts connected to the terminals of scribed. the local circuit, apair of contacts connected THEO. N. VAIL.

5 to points on opposite sides of the metallic JOHN A. SEELY.

circuit, one of said pairs of contacts being located between the otherpair, and a Wedge of *itnesses:

J 0s. KAVANAGH,

insulating material normally separating one i M. H. BAKER.

